70 new rogue planets discovered in our galaxy

Date:
December 22, 2021
Source:
ESO
Summary:
Rogue planets are elusive cosmic objects that have masses
comparable to those of the planets in our Solar System but do
not orbit a star, instead roaming freely on their own. Not many
were known until now, but a team of astronomers, using data from
several European Southern Observatory (ESO) telescopes and other
facilities, have just discovered at least 70 new rogue planets
in our galaxy. This is the largest group of rogue planets ever
discovered, an important step towards understanding the origins
and features of these mysterious galactic nomads.



FULL STORY ========================================================================== Rogue planets are elusive cosmic objects that have masses comparable
to those of the planets in our Solar System but do not orbit a star,
instead roaming freely on their own. Not many were known until now,
but a team of astronomers, using data from several European Southern Observatory (ESO) telescopes and other facilities, have just discovered
at least 70 new rogue planets in our galaxy. This is the largest group
of rogue planets ever discovered, an important step towards understanding
the origins and features of these mysterious galactic nomads.


==========================================================================
"We did not know how many to expect and are excited to have found
so many," says Nu'ria Miret-Roig, an astronomer at the Laboratoire d'Astrophysique de Bordeaux, France and the University of Vienna, Austria,
and the first author of the new study published today inNature Astronomy.

Rogue planets, lurking far away from any star illuminating them,
would normally be impossible to image. However, Miret-Roig and her
team took advantage of the fact that, in the few million years after
their formation, these planets are still hot enough to glow, making them directly detectable by sensitive cameras on large telescopes. They found
at least 70 new rogue planets with masses comparable to Jupiter's in a star-forming region close to our Sun, in the Upper Scorpius and Ophiuchus constellations [1].

To spot so many rogue planets, the team used data spanning about 20 years
from a number of telescopes on the ground and in space. "We measured the
tiny motions, the colours and luminosities of tens of millions of sources
in a large area of the sky," explains Miret-Roig. "These measurements
allowed us to securely identify the faintest objects in this region,
the rogue planets." The team used observations from ESO's Very Large
Telescope (VLT), the Visible and Infrared Survey Telescope for Astronomy (VISTA), the VLT Survey Telescope (VST) and the MPG/ESO 2.2-metre
telescope located in Chile, along with other facilities. "The vast
majority of our data come from ESO observatories, which were absolutely critical for this study. Their wide field of view and unique sensitivity
were keys to our success," explains Herve' Bouy, an astronomer at the Laboratoire d'Astrophysique de Bordeaux, France, and project leader of
the new research. "We used tens of thousands of wide-field images from
ESO facilities, corresponding to hundreds of hours of observations, and literally tens of terabytes of data." The team also used data from the European Space Agency's Gaia satellite, marking a huge success for the collaboration of ground- and space-based telescopes in the exploration
and understanding of our Universe.

The study suggests there could be many more of these elusive, starless
planets that we have yet to discover. "There could be several billions
of these free- floating giant planets roaming freely in the Milky Way
without a host star," Bouy explains.

By studying the newly found rogue planets, astronomers may find clues to
how these mysterious objects form. Some scientists believe rogue planets
can form from the collapse of a gas cloud that is too small to lead to
the formation of a star, or that they could have been kicked out from
their parent system. But which mechanism is more likely remains unknown.

Further advances in technology will be key to unlocking the mystery
of these nomadic planets. The team hopes to continue to study them in
greater detail with ESO's forthcoming Extremely Large Telescope (ELT), currently under construction in the Chilean Atacama Desert and due to
start observations later this decade. "These objects are extremely faint
and little can be done to study them with current facilities," says
Bouy. "The ELT will be absolutely crucial to gathering more information
about most of the rogue planets we have found." Notes [1] The exact
number of rogue planets found by the team is hard to pin down because
the observations don't allow the researchers to measure the masses of
the probed objects. Objects with masses higher than about 13 times the
mass of Jupiter are most likely not planets, so they cannot be included
in the count.

However, since the team didn't have values for the mass, they had to
rely on studying the planets' brightness to provide an upper limit
to the number of rogue planets observed. The brightness is, in turn,
related to the age of the planets themselves, as the older the planet,
the longer it has been cooling down and reducing in brightness. If
the studied region is old, then the brightest objects in the sample
are likely above 13 Jupiter masses, and below if the region is on the
younger side. Given the uncertainty in the age of the study region,
this method gives a rogue planet count of between 70 and 170.

========================================================================== Story Source: Materials provided by ESO. Note: Content may be edited
for style and length.


========================================================================== Related Multimedia:
* Rogue_planets ========================================================================== Journal Reference:
1. Nu'ria Miret-Roig, Herve' Bouy, Sean N. Raymond, Motohide Tamura,
Emmanuel Bertin, David Barrado, Javier Olivares, Phillip
A. B. Galli, Jean-Charles Cuillandre, Luis Manuel Sarro, Angel
Berihuete, Nuria Hue'lamo. A rich population of free-floating
planets in the Upper Scorpius young stellar association. Nature
Astronomy, 2021; DOI: 10.1038/ s41550-021-01513-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211222153104.htm

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